379 



Professor Shaler. Is the energy of diffusion and the tendency of the females to 

 travel at all proportioned to their numerousness ? 



Professor Riley. Yes; it is a general principle with insects that in proportion as 

 they become unduly multiplied the migratory instinct is developed. 



Professor Shaler. So that in so far as we reduce the number in a given field we 

 tend to reduce the expansive energy ? 



Professor Riley. Without doubt. 



Professor Shaler. And therefore if we fail to exterminate it this year we shall 

 at least diminish its expansive energy. 



Professor Riley described the Cyclone nozzle, stating that it is not on the market, 

 but is easily made by any good mechanic. Thomas Somerville & Son, of Washing- 

 ton, are constantly supplying it. Professor Riley recommended the Vermorel modifi- 

 cation. 



At 6 p. m. the conference adjourned. 



THE RAVAGES OF LIPARIS (PSILURA) MONACHA IN GERMANY 

 AND MEANS OF DEFENSE. 



[Author's abstract of a paper read by B. E. Fernow before the Entomological Soci- 

 ety of Washington, March 5, 1891.] 



Mr. Fernow spoke of the alarmiog increase of Liparis monacha in 

 Germany, and especially Bavaria, during the last year and the anticipa- 

 tions of still greater damage in 1892, and hence the diligent search 

 after effectual remedies. He pointed out that such ravages in German 

 pine and spruce forests meant not only many thousands of dollars loss 

 in depreciation of wood values, but also most inconvenient disarrange- 

 ment of working plans, which are necessarily laid for 100 or more years 

 in advance. 



He referred to the last great ravages of this insect, which involved 

 an area of over 100,000 square miles and to which 55,000,000 cords of 

 wood succumbed in the spruce forests of eastern Prussia during the 

 years 1853-'67, necessitating the premature cutting of 7,000,000 cords 

 of wood to save it from subsequent attacks of Scolytids. In the pres- 

 ent case some 20,000 acres of spruce in Upper Bavaria were first at- 

 tacked, but soon reports from all parts of Germany, Austria, Bohemia, 

 €tc., indicated unusual increase, so that many thousand square miles of 

 forest are involved. In the first-named district over $8,000 were spent 

 toward checking the damage. 



A special commission has been appointed by the Bavarian Govern, 

 ment to discuss the measures to be taken against the further spread of 

 lAparis monacha and the amount of observations and intelligent pre- 

 liminary discussion of measures in the ''Programme for the Commis- 

 sion " is said to be one of the most comprehensive works touching such 

 a subject. 



Of the life history of the insect Mr. Fernow pointed out only the fol- 

 lowing notes of interest: 



Like most of the North European Bombycids, it has but one genera- 



